The present invention relates generally to a fastener and, more particularly, to a fastener for attaching a first panel to a second panel. Specifically, the present invention relates to a fastener for attaching sundry interior and exterior panels or components together in a myriad of applications.
Threaded, push-on fasteners are well known in the art and are used in the assembly of panels or components together in a wide range of applications. By way of example, such fasteners find use in attaching various trim panels and moldings to sheet metal in the manufacture of automobiles or other vehicles and articles of manufacture such as trucks, tractors, construction equipment, boats, etc. Such fasteners are particularly useful in the attachment of side wall trim panels; head liner trim panels; trunk trim panels; shelf trim panels; garnish molding; seat panel trim; coat hooks, etc. External applications include the attachment of exterior moldings; lights; and metal trim. The aforementioned recitation is not exhaustive and many other applications exist in which push-on fasteners represent a convenient and efficient method for attaching components together.
In practice, for example, such as in the attachment of automotive interior door trim panels to interior sheet metal body panels, aligned pairs of assembly apertures are typically formed to extend through door trim panels and the metal body panels to which they attach at appropriate locations. Fasteners (also interchangeably referred to herein as xe2x80x9cretainersxe2x80x9d or xe2x80x9cclipsxe2x80x9d) are inserted through such co-aligned apertures of the trim panels and metal body panels to securely fasten the trim panels in place. Each clip generally includes a head and an elongate dependant shaft. The head of each clip is positioned against an outward surface of the trim panel surrounding the trim panel aperture or otherwise affixed to the trim panel by alternative fastening means such as a plastic bolt, a screw, or molded into the plastic or rubber panel itself. The clip shaft is sized to project through the sheet metal aperture and includes a series of outwardly directed, spaced-apart tines that engage peripheral edges defining the sheet metal aperture. The tines of the clip are spaced along the longitudinal axis of the shaft and sequentially engage the peripheral edges of the sheet metal aperture as the shaft is inserted through the aperture. Accordingly, the user can, by varying the extent to which the shaft is inserted into its respective sheet metal panel aperture, adjust the spacing between the trim panel and the sheet metal panel to which it attaches. The clip, as a result, can be utilized to fasten trim panels to sheet metal panels of variable thicknesses.
The tines of known retainers are thin-walled plastic fingers that generally circumscribe a cylindrical shaft and have a bias toward the head of the fastener. The tines are spaced at regular intervals along the longitudinal axis of the shaft. The diameter of the shaft from tine tip to tine tip is sized to protrude through an aperture of the sheet metal panel with interference. The bottom surface of the tines slide over the peripheral edges of the sheet metal apertures as the shaft of the fastener is inserted. The bottom biased surface of the ribs minimizes resistance between the shaft and the peripheral sheet metal edges and thereby reduces the force necessary to effectuate insertion of the retainer shaft. As mentioned previously, the tines have a bias toward the head of the fastener such that, upon insertion through a respective sheet metal panel aperture, the tip of each tine is biased against outward sides of the sheet metal panel to resist withdrawal of the retainer shaft from its respective sheet metal aperture. The requisite force necessary to insert the retainer shaft into a sheet metal aperture and to withdraw the shaft therefrom are influenced by multiple variables, including the angle of bias of the tines and the material composition thereof, and the diameter of the aperture relative to the shaft external diameter.
Commercially available fasteners are typical composed of thermoset plastic or thermoplastic composition. The fasteners are formed unitarily by conventional manufacturing processes such as injection molding. Plastic composition allows the fasteners to be manufactured economically and further provides the retainer shaft tines with sufficient resiliency to facilitate their reciprocal travel within a respective sheet metal panel aperture. In the reverse, withdrawal direction, an application of an axially directed extraction force to the head of the retainer pulls the tines of the retainer shaft against outward edge surfaces of the sheet metal panel until the tines undergo a deformation in the reverse direction. Deformation of the retaining tines away from the retainer head allows the retainer shaft to be pulled, generally with difficulty, out of the sheet metal aperture. Subsequent to withdrawal, the resilient shaft tines reconfigure back to their original configuration and resume their bias toward the fastener head. The fastener may then be reused by reinserting the shaft into its respective sheet metal aperture in a forward direction.
It is customary in the manufacture of automobiles to attach and detach the trim panels from the sheet metal panels at several junctures in the assembly process. The trim panels may further require removal during the testing phase of an automobile""s assembly to allow for final inspection repairs. To attach and detach the trim panels, the fasteners are inserted into and withdrawn from respective sheet metal apertures as described previously. The plastic composition of conventional fasteners provide the shaft tines with sufficient resiliency with which to allow the tines to compress inward and pass through the slightly undersized sheet metal panel apertures. Unfortunately, however, the edges of the sheet metal apertures are frequently rough and uneven and may include sharp-edged burrs. Repeated insertion and extraction of the retainer shaft tines against such sharp metal edges can cause destruction of the retainer shaft tines or a permanent deformation resulting in a degradation in their performance. Consequently, by the end of the assembly process, the retainer tines may be damaged to the point of necessitating a replacement of the fastener, adding to the cost of the assembly. Alternatively, the fasteners may remain in use but be damaged to the point of providing a less than positive attachment of the trim panel to the sheet metal panel.
A secondary disadvantage to conventional plastic fasteners is that the force required to insert the fastener through a sheet metal aperture or extract the fastener therefrom is greater than optimally desired. The relatively high insertion force and extraction force required in known fasteners can and does, as a result, cause user fatigue and/or injury. Moreover, the insertion and extraction forces for conventional fasteners is fixed and may not be satisfactory for all the myriad applications to which the fastener may find use. In short, the insertion and extraction force of known fasteners is not variable or easily altered which limits the utility of the device in may applications.
Yet a further disadvantage inherent in conventional fasteners is that they are limited in the range of adjustment which they afford in the spacing between the trim panel and the sheet metal panel. The tines along the fastener shafts of conventional clips, due to their biased orientation, are spaced at rather large centerline to centerline gradations. As discussed previously, the fastener adjusts to variable thicknesses of sheet metal by varying the extent to which the fastener shaft is inserted into its respective sheet metal panel aperture. Relatively large tine-to-tine spacing found in conventional fastener shafts provides a less than desired range of adjustment. Accordingly, the user may not be able to position the fastener shafts within their respective sheet metal panel apertures at the precise location providing the desired spacing between the trim panel and the sheet metal body panel.
Thus, the need exists for a push-on fastener for attaching trim panels to sheet metal panels that is durable and capable of withstanding repeated frictional insertion and withdrawal from sheet metal apertures. Such a fastener must further provide a high range of adjustment and require relatively low insertion and withdrawal forces. In addition, the fastener must provide a head configuration that is readily modified to accommodate various methods of connection with a trim panel. Ideally, the insertion and extraction force in a suitable fastener would be readily varied to accomodate use of the fastener in myriad applications.
It is, therefore, an object of the present invention to provide a push-on fastener for attaching one panel to a second panel.
It is another object of the present invention to provide a push-on fastener, as above, requiring a relatively low insertion and a variable extraction force that will not damage the fastener or parts which are connected by the fastener that may be readily varied or reconfigured to accomodate fastener use in sundry applications.
It is yet another object of the present invention to provide a push-on fastener, as above, that is durable and capable of withstanding repeated insertion and extraction cycles without sustaining damage or suffering a degradation in performance.
A further object of the present invention is to provide a push-on fastener, as above, having a capability for attaching to panels of variable thicknesses.
Yet another object of the present invention is to provide a push-on fastener, as above, having a plurality of head configurations for alternative means of attaching the one panel to the second panel.
A further object of the present invention is to provide a push-on fastener, as above, that is economical to manufacture and convenient to install.
Another object of the present invention is to provide a push-on fastener having a fastener head configuration that is readily modified to accommodate various methods of connection with a trim panel.
These and other objects of the present invention, as well as the advantages thereof over existing prior art fasteners, which will become apparent from the description to follow, are accomplished by the improvements hereinafter described and claimed.
A preferred exemplary embodiment and alternative embodiments incorporating the concepts of the present invention are shown by way of example in the accompanying drawings without attempting to show all the various forms and modifications in which the invention might be embodied, the invention being measured by the appended claims and not by the details of the specification. As described, the invention comprises a fastener having a head portion at an upper end and an elongate shaft depending therefrom. The shaft comprises a plurality of spring legs, each leg having one end affixed to the head portion at a bend and an opposite end depending from the head portion. The legs are formed from a malleable, resilient material such that each leg flexes resiliently inward and outward relative to the head portion. Each leg further is formed to provide at least one outwardly projecting locking rib; the locking rib comprising an inclined leading surface, a trailing locking surface, and a peak surface disposed between the leading surface and the locking surface. Insertion of the fastener shaft into an appropriately undersized aperture establishes an inward flexing of the shaft legs. As the locking rib clears the aperture, the leg flexes outward and the locking rib locks the fastener within the aperture.
The insertion and extraction force required by the fastener may be adjusted by varying the angle of leading and trailing surfaces of the locking rib; the spring properties of the material that forms the shaft legs; and/or the bend angle at which the shaft legs connect to the fastener head. Accordingly, a further aspect of the invention is a method of forming an adjustable fastener composed of a malleable material. The method comprises the steps of forming a head portion in a first plane; forming at least one resilient spring leg to depend from the plane of the head portion at a bend; forming at least one locking rib along the spring leg; and adjusting the angle at which the spring leg bends from the plane of the head portion to alter the insertion and extraction force characteristics of the fastener.